X-ray scans for detecting hollow heart in potatoes

A study was conducted to determine whether hollow heart potatoes might be separated from normal ones by a nondestructive method based on an objective criterion. The profile of x-ray density measured along the longitudinal axis of each of 106 tubers was recorded and then analyzed by computer. The second derivative of the x-ray density profile provided a basis for detecting hollow heart. All of the defective tubers were separated without inclusion of any normal tubers. The incidence of hollow heart was 21.4%.     

Relationships of hollow heart in Irish potatoes to carbohydrate reabsorption and growth rate of tubers

Tubers of Irish Cobbler that were hollow grew faster than non-hollow tubers on the same plant. However, tubers of varieties without hollow heart grew just as rapidly as tubers of the variety with hollow heart. Therefore tuber growth rate was related to hollow heart occurring within a variety but could not account for differences between varieties. When plant foliage was pruned the C-¹⁴ label from sucrose was translocated from the tuber to the top of the plant. Our studies suggest hollow heart can occur in small tubers under the following conditions: (i) moisture stress in the tubers resulting in conversion of starch to sugar, followed by a rapid influx of water into the tuber resulting in rapid enlargement of the perimedullary zone and a separation in the pith that later develops into hollow heart, and/or (ii), following injury to some cells in the tuber due to reabsorption of minerals and carbohydrates or depletion of food reserves followed by tuber enlargement. It seems probable however that hollow heart that is initiated in large tubers is only associated with excessively rapid tuber enlargement without the involvement of reabsorption or depletion of food reserves.     

Reducing chilling injury of potatoes by intermittent warming

Potato tubers held continuously 19 weeks at 32 F developed chillinginjury symptoms early during storage and the symptoms worsened with time in storage. Early symptoms included browning and surface mold on skinned areas. By 11 weeks mahogany browning, blackheart, and hollow heart, bluish skin discoloration and sinking of intact skin were visible in daylight. And under ultraviolet light, yellow fluorescence was visible in halos, washes, or spots around or near internal tuber tissues discolored by other chilling-injury symptoms. Some damage at 32 F became visible after subsequent holding of tubers for 1 week at 60 F. Tubers accumulated high amounts of reducing and total sugar at 32 F and respiration, measured at 60 F as CO₂ evolved, was progressively stimulated by time at 32 F. Sugar build-up, respiration-rate increase, and chilling injury seemed to show no cause-and-effect relationship but appeared as separate phenomena each caused by the stress of holding tubers at too low a temperature. Moving potatoes to 60 F for 1 week after every 3rd week to interrupt storage at 32 practically eliminated all forms of chilling injury except skin browning and surface mold which were greatly reduced. Sugar content and respiration rates in tubers intermittently held at low and high temperatures were higher after periods in low temperature and lower after periods at 60 F, and in general were maintained at levels much lower than in potatoes held continuously at 32, 36, or 40 F. In all treatments sugar content was higher than desirable for chipping type potatoes. Holding potatoes at 60 F for 1 to 4 weeks before placing them at 32 F reduced skin browning and surface mold but had no effect on other forms of chilling injury, sugar accumulation, or respiration rates in tubers as measured after 15 to 19 weeks continuously at 32 F. Practically no chilling-injury symptom except for very little mold growth and browning of skinned areas developed in tubers held in 36 or 40 F.     

Response of Russet Burbank potatoes to ethephon sprays

Ethephon ((2-chloroethyl)phosphonic acid) was sprayed on the foliage of Russet Burbank potatoes at tuber initiation in four separate field trials over two years. Rates were 0, 61, 122 and 183 g ai/ha. Total yield, yield of U.S. No. 1’s, hollow heart and brown center generally decreased at higher ethephon rates. Yield of undersized tubers increased. Ethephon sprays generally decreased specific gravity but the effect was minor and not consistent. In three of the four plantings where hollow heart and brown center in the untreated controls exceeded 8 t/ha, the low rate of ethephon increased the yield of non-hollow tubers ≥56 g in size.     

Effect of seed piece population on the yield and processing quality of Russet Burbank potatoes

The effect of seed piece population on tuber yield, size distribution and processing quality of Russet Burbank potatoes grown under nonirrigated conditions in southern Manitoba from 1983 to 1987 was determined. Seed pieces were planted at 21.7, 26.3, 33.3 and 45.5 thousand seed pieces per hectare, and plant emergence generally exceeded 90% of the seed piece population. Marketable tuber (greater than 5 cm in diameter) yields were not affected by seed piece population. As population increased, however, the number of harvested tubers increased and average tuber size decreased, which resulted in a decreased yield of premium tubers (greater than 284 g) and an increased yield of small tubers (less than 5.0 cm in diameter). Specific gravity, the incidence of hollow heart in maingrade (5 cm in diameter to 284 g in weight) and premium tubers, and fry color were not significantly affected by seed piece population. In the one trial tested, sucrose content decreased as population increased, however, this was not reflected in improved fry color after storage.     

The relationship between tuber size and hollow heart in Norgold Russet potatoes

Hollow heart (HH) when found in potatoes is predominately in the largest tubers. Various tuber lots of cv Norgold Russets ranged from 3.4 to 55.9% HH by weight. In the lot with the least HH approximately 43% of the tubers over 8.89 cm in diameter were hollow compared to 0.2% of those between 3.81 and 5.07 cm. By first removing the very largest, followed by successively smaller tubers there was a continuous reduction in HH in all tuber lots. There were only small differences among the five years in the effect of sizing on HH, and these appeared to be associated with yield differences among years. Figures illustrate the specific effect of removing progressively smaller tubers on the amount of HH remaining.     

Electron microprobe and neutron activation analysis for the determination of elemental distribution in hollow heart potato tubers

Electron microprobe and neutron activation analysis were used to evaluate the distribution of elements within potato tubers having the physiological disorder hollow heart. Both methods of analysis correlated well for all elements tested. In hollow heart tubers, there were significantly higher Ca⁺⁺ levels in the stem end than in the bud end; however, a Ca⁺⁺ gradient in the control was not evident. The stem to bud end ratios for Ca⁺⁺ were highest in the hollow heart tubers. A Cl^? gradient from stem to bud end was obvious in both the hollow heart and control tubers. In the control tubers, K⁺ was highest in the bud end and lowest in the stem end. There was no K⁺ gradient in hollow heart tubers, but in the area adjacent to the hollow it was higher than at both ends.     

Relationships between weather,plant spacing and the incidence of hollow heart in Norgold Russet potatoes

Partial regression analysis of ten years’ data showed the percent of hollow heart (HH) tubers by weight in Norgold Russet potatoes increased with an increase in number of days and rainfall between tuber initiation and plant killing, and decreased with an increase in plant population and degree day accumulation during the same period. Highly significant third order partial correlation coefficients for these variables with percent HH were: days between tuber initiation and plant killing 0.699, rainfall between tuber initiation and plant killing 0.320, plant population -0.530 and degree day accumulation between tuber initiation and plant killing -0.753. When these variables were used in a multiple linear regression model with% HH as the dependent variable the coefficient of determination (R²) was 0.72. The model was not significantly improved by including solar radiation, yield of tubers, number of tubers, or soil moisture at tuber initiation as other independent variables.     

Expression of hollow heart in segregating tetraploid potato families

Expression of hollow heart, a physiological disorder in potato, is controlled by both genotype and environment. Development of high levels of resistance in cultivars would reduce economic yield losses that occur under conditions that promote hollow heart. This experiment was conducted to study hollow heart in segregating populations from parents in a breeding program. Nine families were planted in a replicated trial under dryland conditions and five of those families were also grown at an irrigated location under conditions favoring the expression of hollow heart. As expected, positive correlations between hollow heart and both mean yield and tuber weight were detected; correlations between hollow heart and tuber number were negative. Hierarchical regression analysis was performed on these yield traits to determine the independent contribution of each to the overall results. The highest levels of hollow heart were found in families with susceptible parents, but susceptible clones were obtained in families with two resistant parents. Regardless of the type of cross, selection of clones with large tubers increased the probability of selecting for susceptibility to hollow heart.     

Relationships between tuber size and time of harvest to hollow heart initiation in Dryland Norgold Russet potatoes

In four years of field trials approximately75% of hollow heart was initiated in tubers between 5.1 and 7.6 cm in diameter. Only rarely was hollow heart initiated in tubers less than 3.8 cm. The frequency of hollow heart was approximately nine times greater in medium sized tubers (6.4 to 7.6 cm) and 34 times greater in large tubers (over 7.6 cm) than in small tubers (5.1 to 6.4 cm). The number of tubers with hollow heart increased linearly through the last five weeks of the growing season. Hollow heart during the four years ranged from 4200 to 31900 tubers/ha or 2.9 to 13.0% of all tubers over 2.5 cm. There were consistent increases in tuber growth between harvests in each season, inferring an absence of severe plant stress and supporting the hypothesis that hollow heart was due to tissue tension associated with tuber enlargement.     

The incidence of decay and factors affecting bacterial soft rot of potatoes

The incidence of tuber decay in rail car shipments of potatoes from the State of Washington was determined from 1965 to 1969 inclusive. Reinspection certificates revealed that 7.9% of the rail cars of potatoes shipped during this period were rejected due to tuber defects; tuber decay accounted for 63% of these rejected cars. Percentage of rejections due to tuber decay was greater for Russet Burbank than for Norgold Russet potatoes. Temperature, moisture, and oxygen levels influenced development of bacterial soft rot in freshly harvested potatoes and in potatoes stored for 3 months at 35 F (2 C) previous to treatment. When tuber surfaces were kept dry, no soft rot developed in 11 days over ranges of 50–70 F (10–21 C) and 2–20.5% oxygen levels. Freshly harvested tubers partially immersed in water did not rot when cooled to 40 F (4.4 C) in < 24 hours and held for 8 days under either 20.5 or 4% oxygen levels; however, tubers, rotted when stored similarly but at 50 F or higher temperatures. Partially immersed tubers incubated for 1 day or longer at 70 F developed soft rot in a low oxygen (4%) when later stored for, 8 days at 40 F. When rot occurred, the amount was always greater under lower oxygen levels irrespective of storage temperature. Of various cooling methods tested in rail cars loaded with 100 lb (45.4 kg) sacks of potatoes, prechilling of tubers and icing of cars prior to loading lowered floor temperatures most rapidly. Icing cars after loading lowered floor temperatures the slowest. In a carton shipment, the temperature remained above 68 F (20 C) in cartons after 8 days in transit, even though the wall and floor temperatures had cooled to near 55 F (12.8 C) by the second day. Oxygen level surrounding, tubers in the center of car loads of 100 lb sacks of potatoes was approximately 20.5% after 8 days transit.     

The effect of water stress on the yielding capacity of potato crops and subsequent performance of seed tubers

Summary The effect of water stress on yielding capacity of potatoes was studied in 3 years using four different levels of soil water potential (0.7, 1.9, 3.4 and 7.8 atm.) in experiments in specially adapted structures that excluded uncontrolled water supply. Seed tubers from these crops were planted in the following years to investigate effects of water stress on their subsequent performance. Limited soil moisture availability decreased yield and the number and size of tubers. The growing period was shortened by 1–4 weeks and dormancy period by 2–8 weeks. In the following year, seed produced under conditions of moisture stress gave plants with 20% fewer stems. 24–33% less yield, 18–22% fewer tubers and 19–22% fewer large tubers than plants from seed produced under abundant water supply. It is concluded that the yield potential of seed tubers can be improved by careful attention to the availability of soil moisture during their production.     

Effect of seed tuber and seed piece size on growth and incidence of hollow heart in Norgold Russet potatoes

Small seed pieces decreased yield and number of tubers. Both seed tuber and seed piece size affected the percentage of tubers with hollow heart. Hollow heart increased from 14 to 22% as the seed tuber size increased from 57 to 228 g and decreased from 27 to 19% as the seed piece size increased from 28 to 57 g. The least hollow heart (11%) occurred in tubers of plants grown from 57 g whole seed pieces and the most (26%) in tubers of plants grown from 228 g seed tubers cut into 28 g seed pieces. Hollow heart was positively correlated with the mean tuber size and negatively correlated with the number of mainstems per hill, total yield, and total number of tubers.     

Specific gravity of Russet Burbank potatoes

Variability in specific gravity of Russet Burbank potatoes was documented in a single 32 hectare field. Maximum variation was 40 units among individual tubers within hills (one unit equals one part in 1000th of specific gravity measurement) and 15 units among hills. Field site variability of 10–15 units was common between sampled grid lines in the field; but bulked samples (truckloads) reduced the sampled variability to 8–10 units. When the samples were taken from bulked lots as opposed to single hill samples, the variability decreased. Grower lots, which were pooled samples from several truckloads, showed specific gravity differences of 2–7 units even though all lots were from the same field. These variations among specific gravity samples should be taken into account when considering total solids content in any lot of potatoes. Degree of russetting of the skin and hollow heart also influenced specific gravity measurements. Measured differences between peeled and unpeeled lots of 10 units in specific gravity corresponded to 2% difference in total solids content. Statistically, the variance of the peeled lot was one half that of the unpeeled lot, therefore, to minimize the measured differences due to skin type, peeled potatoes could be used for the specific gravity measurements.     

Effect of two plant growth regulators on the yield and quality of russet burbank potatoes

Summary Foliar applications of ethephon (ETH) 300 g a.i. ha⁻¹; chlormequat chloride (CCC) 920 g a.i. ha⁻¹, with a second application of 230 g a.i. ha⁻¹ approximately 2 weeks later; and a mixture of the two (ETH/CCC) 156 g a.i. ethephon and 299 g a.i. chlormequat chloride ha⁻¹ were made to field-grown Russet Burbank potatoes in 1986, 1987 and 1989. All the treatments increased the number of tubers set and reduced the average tuber weight compared to the control resulting in a reduction in premium and marketable tubers, and an increase in small tubers. Differences were greatest for ETH and least for CCC. ETH and ETH/CCC decreased the specific gravity, increased the incidence of deformities, and decreased the incidence of tubers with hollow heart. The growth regulators did not affect fry colour.     

Factors influencing reconditioning of Russet Burbank potatoes

Studies were made to determine factors which influence reconditioning of Russet Burbank tubers. Tubers from plants grown under low fertility were more difficult to recondition than tubers from plants adequately fertilized. Low specific gravity potatoes were also more difficult to recondition than high specific gravity potatoes even though the initial sugar content was approximately equal. The stem portion of Russet Burbank tubers lost considerably less sugars than the bud portion during the reconditioning process. It appears that factors which are responsible for high sugar development are also responsible for difficulty in sugar loss. Results also indicate greater difficulty in reconditioning early in the storage period with the loss of sugars becoming easier as the storage season progressed into spring.     

Some anatomical and physiological potato tuber characteristics and their relationship to hollow heart

The inception site of hollow heart (HH) and possible relationships between HH and physiological or anatomical characteristics of tubers were investigated. Scanning electron micrographs revealed cells at the site of HH inception were physically rather than enzymatically degraded. Transmission electron micrographs of tuber pith cells from non hollow (NH) tubers showed cell wall and cytoplasm width varied among cultivars but were not related to HH resistance. Water potential of NH tuber tissues at the pith, bud, center and stem end of 3 cultivars and one selection varying in resistance to HH was determined. Although the water potential gradually became less negative as tubers advanced in maturity, no differences were found in water potential between pith cells in various parts of tubers or among cultivars. Tuber pith cells increased in size concomitant with tuber growth. In all tubers pith cells were largest in the center and stem end and smallest in the bud end, but differences in mean pith cell size among cultivars were not related to HH susceptibility. However, within a cultivar the bud, center, and stem end pith cells of HH tubers were all smaller than the corresponding pith cells from similarly sized NH tubers.     

Irrigation and soil temperature effects on Russet Burbank quality

Potato growers in the Pacific Northwest suffer large economic losses in seasons with above normal temperatures, due to excess reducing sugars in tubers, which cause dark-end French fries. Our objective was to study irrigation management effects on potato quality, particularly the factors causing dark-end French fries or sugar-end syndrome. Solid-set sprinkler irrigated plots were established on potatoes at Kimberly, Idaho during the 1987, 1988 and 1989 irrigation seasons, and at Parma, Idaho in 1987 and 1988. Irrigation treatments were high and low frequency (3/week and I/week) and two or three water application amounts referenced to estimated evapotranspiration (ET, ET+20%, and ET-20%). Neither frequency nor amount significantly affected yields. Irrigation frequency had more influence on potato quality than application amount. More frequent irrigation produced slightly higher quality tubers and lower incidence of dark-ends when fried. Soil temperature was inversely related to tuber grade quality and directly related to percentage of sugar-end tubers. Soil temperature was about 0.5 C lower under the high frequency than under the low frequency irrigation regime. On these silt loam soils, allowing available soil water to decline to 50 percent had no adverse affect on yield or quality.     

Slug damage and control of field slug (Deroceras reticulatum (Müller)) by carvone in stored potatoes

Summary After a wet autumn and harvesting under wet conditions, slugs brought into potato stores via clods and soil adhering to tubers may cause substantial damage by feeding on the tubers. A carvone sprout inhibitor, Talent^?, applied in the potato stores at a dose of 50 ml per tonne potatoes, controlled slugs within a few days. A dose of 25 ml carvone was insufficient. Using a laboratory box test, the slug (Deroceras reticulatum) affected only wounded tubers and, although slime was present on the unwounded potatoes, they were not damaged by slugs.     

Gamma irradiation of potatoes: Effects on sugar content,chip color,germination, greening,and susceptibility to mold

Russet Burbank potatoes that had been stored at 40°F. for 5 months after harvest were irradiated with 5,200 and 14,000 rad of Co⁶⁰ gamma rays. In general, irradiation caused an accumulation of sugars. At 40°F., the sucrose level rose to nearly 3 times that of the control in 16 days following irradiation. Fructose and glucose showed smaller increases and the latter did not accumulate significantly in the tubers given the higher dose of gamma rays. At 70°F., the levels of sucrose and glucose in the irradiated tubers rose above those in the controls, the difference reaching a maximum in 4 days and then declining. Irradiation had no effect on loss of fructose at this temperature. Color of potato chips processed from the irradiated potatoes was in general darker than that of chips from control tubers. The storage-time pattern of color change resembled that of the reducing rather than total sugar. Fourteen thousand rad did not prevent initiation of germination in the tubers but did destroy their sprout-growth apparatus. Although the lower dosage did not prevent initiation and subsequent growth, it prevented the formation of secondary tubers, which appeared on the sprouted control tubers. Furthermore, unlike the controls, the low-dosage potatoes developed branching hair sprouts with no tendency toward apical dominance during the early stages of sprouting. The rate of greening of gamma-irradiated and illuminated tubers was significantly less than that of unirradiated illuminated controls. Evidence is presented that irradiation may increase the susceptibility of potatoes to attack by molds under some conditions.